# Integration of Nonlinear Disturbance Observer within Proxy-based Sliding Mode Control for Pneumatic Muscle Actuators

## TL;DR

This paper introduces a novel control approach combining a nonlinear disturbance observer with proxy-based sliding mode control to enhance the robustness and reduce chattering in pneumatic muscle actuators, validated through extensive experiments.

## Contribution

It proposes a new integrated control method that effectively handles uncertainties and nonlinearities in PMAs, improving tracking accuracy and robustness over existing methods.

## Key findings

- Reduced chattering in control signals
- Enhanced robustness against disturbances
- Validated performance through extensive experiments

## Abstract

This paper presents an integration of nonlinear disturbance observer within proxy-based sliding mode control (IDO-PSMC) approach for Pneumatic Muscle Actuators (PMAs). Due to the nonlinearities, uncertainties, hysteresis, and time-varying characteristics of the PMA, the model parameters are difficult to be identified accurately, which results in unmeasurable uncertainties and disturbances of the system. To solve this problem, a novel design of proxy-based sliding mode controller (PSMC) combined with a nonlinear disturbance observer (DO) is used for the tracking control of the PMA. Our approach combines both the merits of the PSMC and the DO so that it is effective in both reducing the ``chattering" phenomenon and improving the system robustness. A constrained Firefly Algorithm is used to search for the optimal control parameters. Based on the Lyapunov theorem, the states of the PMA are shown to be globally uniformly ultimately bounded. Extensive experiments were conducted to verify the superior performance of our approach, in multiple tracking scenarios.